1. Field of the Invention
This invention relates generally to resilient systems, and more particularly, to a resilient air foil arrangement that has a variable aerodynamic configuration.
2. Description of the Design Challenges
Designing an adaptive control surface for a rotorcraft poses significant challenges. The primary challenge is to design an efficient structure that can distribute local actuation power to the surface of the airfoil to produce a specified shape change. This system must provide the appropriate shape control over the adaptive surface while meeting power, weight, packaging, and survivability constraints. Due to the challenge of rotorcraft systems, one must address the following design criteria:
Shape Morphing                D-Spar location        Required shapes for stall elimination        Wear strip location (top-bottom % chord)        Compliant structure topology/geometry to effect shape change        
Power Required to Achieve Deflection:                Pressure loading        Required deflection (10°, 5°)        Response time (5 Hz to 7 Hz)        Required compliant structure stiffness (aeroelastic and dynamic constraints)        
Packaging Issues:                Available actuator power density (ultrasonic rotary, electromagnetic, inchworm, etc.)        D-Spar location        Actuator system geometry—must move with flap (maximize available space)        
Functionality:                Structural integrity of LE flap        Dynamic/Aeroelastic response & fatigue loading        
The process of designing a compliant structure leading edge flap is a highly inter-disciplinary process that involves aerodynamics, structural mechanics, and kinematics. These components are all interrelated such that the final compliant structure design depends heavily on all three (FIG. 1). Essentially, aerodynamic analysis drives the ideal aerodynamic shapes and predicts the pressure distributions experienced by these shapes. Kinematics relates to shapes that are achievable given design limitations such as restricting elongation of the surface perimeter and minimizing curvature transitions that relate to structural stress. Note that the structure may be optimized around an intermediate target shape (called the medial strain position) that reduces forces and stresses over the entire shape change envelope. This places added importance on the target shape design as the medial strain shape must be able to accurately morph into the extreme target shapes.